If you claimed R&D tax relief a few years ago and assume the process is unchanged, you are working from an old rulebook. The separate SME and RDEC schemes are gone, replaced by a single merged scheme. There is now a notification form that can kill a valid claim before you file it, and HMRC checks claims far harder than it used to. Get the mechanics wrong and you lose the relief.
TL;DR: For accounting periods starting on or after 1 April 2024, most UK companies claim R&D tax relief through the merged scheme at a 20% above-the-line credit, worth roughly 15p to 16.2p per pound after corporation tax. Loss-making R&D-intensive SMEs can get up to 27p. First-time claimants must file a claim notification within six months of their period end, and every claim needs an Additional Information Form or HMRC rejects it.
What Changed With the Merged R&D Scheme?
For accounting periods beginning on or after 1 April 2024, the separate SME and RDEC schemes were merged into one. Almost every company now claims through a single set of rules, regardless of size (BDO, 2025).
The credit is an "above-the-line" receipt. That means it appears as taxable income in your accounts, then reduces your corporation tax bill, rather than working as an extra deduction the way the old SME scheme did. The shift matters for how you present the benefit in your accounts and forecasts.
Two other changes landed alongside. Contracted-out R&D now sits with the company that decides to do the work and bears the risk, not the subcontractor. And overseas subcontractor and externally provided worker costs are restricted, bar narrow exceptions where the work genuinely cannot be done in the UK.
What Is the R&D Tax Relief Rate in 2026?
The merged scheme pays a 20% credit on your qualifying R&D expenditure. Because the credit is taxed as income, the net benefit lands at roughly 15p per pound for a company paying the 25% main corporation tax rate, rising to about 16.2p for a company paying the 19% small profits rate.
So a company spending £200,000 on qualifying R&D and paying the main rate would see a net benefit of around £30,000. The exact figure depends on your tax position and any restriction on your qualifying costs.
In our experience, the most common mistake here is treating the headline 20% as the cash figure. It is a gross rate. Model the after-tax number before you promise a director what the claim is worth, because the difference between 20% and 15% on a large spend is real money.
Enhanced Support for R&D-Intensive SMEs
Loss-making SMEs that spend heavily on research get a better deal through Enhanced R&D Intensive Support (ERIS). To qualify, your R&D spend must be at least 30% of your total expenditure for the period, a threshold reduced from 40% for periods starting on or after 1 April 2024 (HMRC CIRD123000, 2024).
ERIS gives an 86% additional deduction on qualifying costs, and losses can be surrendered for a 14.5% payable credit. Together that is worth up to 27p per pound of R&D spend, a meaningful margin over the merged scheme for a pre-revenue company burning cash on development.
A one-year grace period softens the edge: a company that meets the 30% test one year but dips below it the next can still claim ERIS for that second year. What we see most often is founders who assume they miss out because one quarter was quiet, when the intensity test looks at the whole period.
When Must You Submit a Claim Notification?
This is the deadline that catches people out. If you are a first-time claimant, or you have not made an R&D claim in the previous three years, you must submit a claim notification form to HMRC within six months of the end of your accounting period (GOV.UK, 2025).
Miss that window and the claim is invalid. There is no appeal on the merits and no cash. A company with a 31 December 2025 year-end that needs to notify had until 30 June 2026 to do it.
The form itself is short. It asks for company details, the accounting period, your agent, and a high-level summary of the R&D you intend to claim for. You do not need finished technical reports at this stage, but the summary should match what you file later. One question clients always ask is whether an old, unrelated claim keeps them out of the notification net. If your last claim predates the previous three accounting periods, treat yourself as a new claimant and notify.
Inside the Additional Information Form
Every R&D claim submitted on or after 8 August 2023 needs an Additional Information Form (AIF), filed through HMRC's portal before or with your Company Tax Return (GOV.UK, 2025). File the return without it and HMRC removes the R&D claim from the return.
The AIF asks for a cost breakdown by qualifying category, project descriptions written against the statutory definition of R&D, and the details of the senior internal contact and any agent who helped. For up to three projects you describe them all; for more, you describe those covering the bulk of your spend.
The form is where a weak claim shows. HMRC wants to see a genuine scientific or technological uncertainty and the work done to resolve it, not a marketing description of a new product.
Why Is HMRC Rejecting More R&D Claims?
Because the numbers told it to. HMRC estimated error and fraud in R&D reliefs at 9.9% (£759 million) in 2022-23, falling to 6.5% (£497 million) in 2023-24 and 5.9% (£481 million) in 2024-25 as the crackdown took hold (HMRC, 2024). The legacy SME scheme still ran at 10.6% error and fraud in 2024-25.
HMRC put real resources behind this, moving from around 100 staff on R&D compliance in 2021-22 to more than 500 by 2024-25, against total R&D support of £8.2 billion that year (HMRC Annual Report and Accounts 2024-25).
The upshot for an honest claimant is more scrutiny, not less. A claim that is well documented and defensible passes; a thin one gets a compliance check. Around 90% of non-compliance HMRC finds is error or overreach rather than deliberate fraud, which means good record-keeping is your best protection.
How Should You Prepare a Claim That Survives Scrutiny?
Start with the notification deadline, because it is the one you cannot fix later. Diarise six months after your period end and check whether you need to notify before you do anything else. Fold it into the same calendar as your year-end accounts and corporation tax obligations.
Keep contemporaneous records. Note the technological uncertainties as you hit them, log the time your technical staff spend, and keep the cost workings that feed the AIF. Reconstructing this a year later is where claims get weak, and where a late filing penalty compounds the pain if the return slips too.
Match the technical narrative to a competent professional's view, not a salesperson's. If your finance and development sides disagree on what counts as qualifying, resolve it before you file, not during an HMRC check.
Frequently Asked Questions
Who can claim R&D tax relief under the merged scheme?
UK companies liable to corporation tax that carry out qualifying R&D, seeking an advance in science or technology through work that resolves a genuine uncertainty. Most claim through the merged scheme; loss-making limited companies that are R&D-intensive may use ERIS instead. Sole traders and partnerships cannot claim, as the relief is a corporation tax measure.
What is the deadline to notify HMRC of an R&D claim?
Six months after the end of the accounting period the claim relates to. This applies to first-time claimants and to companies that have not claimed in the previous three years. The claim notification is separate from your Company Tax Return, and missing it makes the whole claim invalid with no route to appeal on the merits.
How much is a merged scheme R&D claim worth?
The credit is 20% of qualifying expenditure. After corporation tax the net benefit is around 15p per pound at the 25% main rate and up to 16.2p at the 19% small profits rate. Loss-making R&D-intensive SMEs using ERIS can reach up to 27p per pound.
Does the Additional Information Form apply to every claim?
Yes. Any R&D claim filed on or after 8 August 2023 must have an Additional Information Form submitted through HMRC's portal before or with the tax return. Without it, HMRC strips the R&D claim out of the return and treats it as never made.
Can my accountant handle the whole R&D claim?
Yes, and the AIF specifically asks for the agent's details. A good adviser checks the notification requirement, tests which scheme applies, prepares the cost analysis, and drafts the technical narrative with your technical lead. The claim still needs input from the people who did the work, since only they can describe the uncertainty they solved.
Not sure whether you need to notify HMRC before your next R&D claim, or whether your project qualifies under the merged scheme? Get in touch - we check the notification deadline, work out which scheme gives you the best result, and prepare the documentation HMRC now expects before it pays.